What makes the α1A -adrenoceptor gene product assume an α1L -adrenoceptor phenotype?

The α_1A -adrenoceptor is abundantly expressed in the lower urinary tract and is the principal therapeutic target for the symptomatic treatment of lower urinary tract symptoms in men. Prazosin has a lower affinity for the lower urinary tract α_1A -adrenoceptor than α_1A -adrenoceptors found in other parts of the body. This has led to the lower urinary tract α_1A -adrenoceptor being subclassified as an α_1L -adrenoceptor. It was demonstrated that this pharmacologically distinct α_1L -adrenoceptor is a product of the α_1A -adrenoceptor gene, but the mechanism by which this altered phenotype is achieved remains a mystery. Hypotheses for this altered pharmacology include the presence of an interacting protein such as cysteine-rich with EGF-like domain (CRELD) 1 or other GPCRs such as the CXCR2 chemokine or 5-HT_1B receptor. Alternatively, the influence of breast cancer resistance protein (BCRP) efflux transporters on the pharmacology of α_1A -adrenoceptors has also been investigated. These and other hypotheses will be described and discussed in this review. LINKED ARTICLES: This article is part of a themed section on Adrenoceptors-New Roles for Old Players. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.14/issuetoc.

NanoBRET: The Bright Future of Proximity-Based Assays

Bioluminescence resonance energy transfer (BRET) is a biophysical technique used to monitor proximity within live cells. BRET exploits the naturally occurring phenomenon of dipole-dipole energy transfer from a donor enzyme (luciferase) to an acceptor fluorophore following enzyme-mediated oxidation of a substrate. This results in production of a quantifiable signal that denotes proximity between proteins and/or molecules tagged with complementary luciferase and fluorophore partners. BRET assays have been used to observe an array of biological functions including ligand binding, intracellular signaling, receptor-receptor proximity, and receptor trafficking, however, BRET assays can theoretically be used to monitor the proximity of any protein or molecule for which appropriate fusion constructs and/or fluorophore conjugates can be produced. Over the years, new luciferases and approaches have been developed that have increased the potential applications for BRET assays. In particular, the development of the small, bright and stable Nanoluciferase (NanoLuc; Nluc) and its use in NanoBRET has vastly broadened the potential applications of BRET assays. These advances have exciting potential to produce new experimental methods to monitor protein-protein interactions (PPIs), protein-ligand interactions, and/or molecular proximity. In addition to NanoBRET, Nluc has also been exploited to produce NanoBiT technology, which further broadens the scope of BRET to monitor biological function when NanoBiT is combined with an acceptor. BRET has proved to be a powerful tool for monitoring proximity and interaction, and these recent advances further strengthen its utility for a range of applications.

NanoBRET ligand binding at a GPCR under endogenous promotion facilitated by CRISPR/Cas9 genome editing

Bioluminescence resonance energy transfer (BRET) is a versatile tool used to investigate membrane receptor signalling and function. We have recently developed a homogenous NanoBRET ligand binding assay to monitor interactions between G protein-coupled receptors and fluorescent ligands. However, this assay requires the exogenous expression of a receptor fused to the nanoluciferase (Nluc) and is thus not applicable to natively-expressed receptors. To overcome this limitation in HEK293 cells, we have utilised CRISPR/Cas9 genome engineering to insert Nluc in-frame with the endogenous ADORA2B locus this resulted in HEK293 cells expressing adenosine A_2B receptors under endogenous promotion tagged on their N-terminus with Nluc. As expected, we found relatively low levels of endogenous (gene-edited) Nluc/A_2B receptor expression compared to cells transiently transfected with expression vectors coding for Nluc/A_2B. However, in cells expressing gene-edited Nluc/A_2B receptors we observed clear saturable ligand binding of a non-specific fluorescent adenosine receptor antagonist XAC-X-BY630 (K_d = 21.4 nM). Additionally, at gene-edited Nluc/A_2B receptors we derived pharmacological parameters of ligand binding; K_d as well as K_on and K_off for binding of XAC-X-BY630 by NanoBRET association kinetic binding assays. Lastly, cells expressing gene-edited Nluc/A_2B were used to determine the pK_i of unlabelled adenosine receptor ligands in competition ligand binding assays. Utilising CRISPR/Cas9 genome engineering here we show that NanoBRET ligand binding assays can be performed at gene-edited receptors under endogenous promotion in live cells, therefore overcoming a fundamental limitation of NanoBRET ligand assays.

Methyl isocyanate inhalation induces tissue factor-dependent activation of coagulation in rats

Methyl isocyanate (MIC) is a highly toxic industrial chemical causing acute lethality after inhalation. The objective of this study was to determine whether alterations in hemostasis also occur in the immediate hours after exposure. Male rats were exposed to MIC (125-500 ppm) by nose-only vapor inhalation for 30 min. Arterial O₂ saturation was monitored prior to exposure, and hourly thereafter. Rats were euthanized at 1, 2, 4, and 8 hr and plasma analyzed for recalcification clotting time, tissue factor (TF) activity, and protein levels. Hypoxemia, as assessed by pulse oximetry, was an early feature of MIC inhalation. In contrast to sham or low (125 ppm) concentrations, 250 and 500 ppm MIC caused significant declines in blood oxygen saturation (% SpO₂) at 1 hr, which remained at deficit during the postexposure period. Commensurate with hypoxemia, plasma clotting time was significantly accelerated 1 hr after MIC inhalation (sham treatment: 955 ± 62.8 s; 125 ppm MIC: 790 ± 62 s; 250 ppm: 676 ± 28.0 s; 500 ppm: 581 ± 175 s). This procoagulant effect was transient, with no difference observed between sham and all MIC groups by 8 hr. Similarly, elevated TF activity and protein were detected in plasma 1 hr after MIC inhalation, each of which showed a progressive decline back to control levels at later timepoints. This study demonstrates that MIC inhalation resulted in hypoxemia and transient hypercoagulability of blood. Accelerated clotting occurred rapidly and was likely due to intravascular TF, which initiates the extrinsic coagulation pathway.

Determination of methyl isopropyl hydantoin from rat erythrocytes by gas-chromatography mass-spectrometry to determine methyl isocyanate dose following inhalation exposure

Methyl isocyanate (MIC) is an important precursor for industrial synthesis, but it is highly toxic. MIC causes irritation and damage to the eyes, respiratory tract, and skin. While current treatment is limited to supportive care and counteracting symptoms, promising countermeasures are being evaluated. Our work focuses on understanding the inhalation toxicity of MIC to develop effective therapeutic interventions. However, in-vivo inhalation exposure studies are limited by challenges in estimating the actual respiratory dose, due to animal-to-animal variability in breathing rate, depth, etc. Therefore, a method was developed to estimate the inhaled MIC dose based on analysis of an N-terminal valine hemoglobin adduct. The method features a simple sample preparation scheme, including rapid isolation of hemoglobin, hydrolysis of the hemoglobin adduct with immediate conversion to methyl isopropyl hydantoin (MIH), rapid liquid-liquid extraction, and gas-chromatography mass-spectrometry analysis. The method produced a limit of detection of 0.05 mg MIH/kg RBC precipitate with a dynamic range from 0.05-25 mg MIH/kg. The precision, as measured by percent relative standard deviation, was <8.5%, and the accuracy was within 8% of the nominal concentration. The method was used to evaluate a potential correlation between MIH and MIC internal dose and proved promising. If successful, this method may be used to quantify the true internal dose of MIC from inhalation studies to help determine the effectiveness of MIC therapeutics.

Automated 3D segmentation of methyl isocyanate-exposed rat trachea using an ultra-thin, fully fiber optic optical coherence endoscopic probe

Development of effective rescue countermeasures for toxic inhalational industrial chemicals, such as methyl isocyanate (MIC), has been an emerging interest. Nonetheless, current methods for studying toxin-induced airway injuries are limited by cost, labor time, or accuracy, and only provide indirect or localized information. Optical Coherence Tomography (OCT) endoscopic probes have previously been used to visualize the 3-D airway structure. However, gathering such information in small animal models, such as rat airways after toxic gas exposure, remains a challenge due to the required probe size necessary for accessing the small, narrow, and partially obstructed tracheas. In this study, we have designed a 0.4 mm miniature endoscopic probe and investigated the structural changes in rat trachea after MIC inhalation. An automated 3D segmentation algorithm was implemented so that anatomical changes, such as tracheal lumen volume and cross-sectional areas, could be quantified. The tracheal region of rats exposed to MIC by inhalation showed significant airway narrowing, especially within the upper trachea, as a result of epithelial detachment and extravascular coagulation within the airway. This imaging and automated reconstruction technique is capable of rapid and minimally-invasive identification of airway obstruction. This method can be applied to large-scale quantitative analysis of in vivo animal models.

From the Cover: ImpairedProliferation and Differentiation of the Conducting Airway Epithelium Associated With Bronchiolitis Obliterans After Sulfur Mustard Inhalation Injury in Rats

Sulfur mustard (SM) is a chemical warfare agent that causes chronic airway remodeling. This study's objective was to assess for changes to the bronchiolar epithelium after SM exposure to explain its contribution to chronic airway remodeling.

Materials and methods

Adult male rats were exposed to a sublethal dose of SM inhalation (1.0-1.2 mg/kg) for 50 min. Histological sections of the bronchiolar epithelium were analyzed for changes using hematoxylin and eosin, trichrome, and immunofluorescent staining for acetylated tubulin (AT) and club cell secretory protein (CCSP). CCSP in bronchoalveolar lavage fluid was assessed using western blot. A bromodeoxyuridine (BRDU) assay was used to assess for epithelial proliferation, and real-time PCR measured changes in Notch mRNA expression.

Results

SM caused significant proximal bronchiolar epithelial injury with epithelial denudation, loss of acetylated tubulin and CCSP staining, and reduced bronchoalveolar lavage fluid CCSP levels. bromodeoxyuridine (BRDU) + staining of proximal bronchiolar epithelial cells was not increased, but staining was increased in the distal bronchiolar epithelium. One month after injury, the proximal bronchiolar epithelium was not fully repaired. Significant collagen deposition surrounded proximal bronchioles with luminal obstruction, consistent with bronchiolitis obliterans. These changes corresponded with a downregulation of Notch1, Notch3, and Hes1 mRNA expressions.

Conclusions

This study demonstrates that SM exposure resulted in severe proximal airway epithelial injury, persistent morphological changes, impaired epithelial proliferation and, ultimately, bronchiolitis obliterans. These changes occurred at the same time that the Notch signaling genes were downregulated. Thus, the lung epithelium and the Notch signaling pathway may be worthy targets for the prevention of chronic airway remodeling after SM inhalation injury.

Oxygen Administration Improves Survival but Worsens Cardiopulmonary Functions in Chlorine-exposed Rats

Chlorine is a highly reactive gas that can cause significant injury when inhaled. Unfortunately, its use as a chemical weapon has increased in recent years. Massive chlorine inhalation can cause death within 4 hours of exposure. Survivors usually require hospitalization after massive exposure. No countermeasures are available for massive chlorine exposure and supportive-care measures lack controlled trials. In this work, adult rats were exposed to chlorine gas (LD_58-67) in a whole-body exposure chamber, and given oxygen (0.8 Fi_O2) or air (0.21 Fi_O2) for 6 hours after baseline measurements were obtained. Oxygen saturation, vital signs, respiratory distress and neuromuscular scores, arterial blood gases, and hemodynamic measurements were obtained hourly. Massive chlorine inhalation caused severe acute respiratory failure, hypoxemia, decreased cardiac output, neuromuscular abnormalities (ataxia and hypotonia), and seizures resulting in early death. Oxygen improved survival to 6 hours (87% versus 42%) and prevented observed seizure-related deaths. However, oxygen administration worsened the severity of acute respiratory failure in chlorine-exposed rats compared with controls, with increased respiratory acidosis (pH 6.91 ± 0.04 versus 7.06 ± 0.01 at 2 h) and increased hypercapnia (180.0 ± 19.8 versus 103.2 ± 3.9 mm Hg at 2 h). In addition, oxygen did not improve neuromuscular abnormalities, cardiac output, or respiratory distress associated with chlorine exposure. Massive chlorine inhalation causes severe acute respiratory failure and multiorgan damage. Oxygen administration can improve short-term survival but appears to worsen respiratory failure, with no improvement in cardiac output or neuromuscular dysfunction. Oxygen should be used with caution after massive chlorine inhalation, and the need for early assisted ventilation should be assessed in victims.

Transplantation of Airway Epithelial Stem/Progenitor Cells: A Future for Cell-Based Therapy

Cell therapy has the potential to cure disease through replacement of malfunctioning cells. Although the tissue stem cell (TSC) is thought to be the optimal therapeutic cell, transplantation of TSC/progenitor cell mixtures has saved lives. We previously purified the mouse tracheobronchial epithelial TSCs and reported that in vitro amplification generated numerous TSCs. However, these cultures also contained TSC-derived progenitor cells and TSC repurification by flow cytometry compromised TSC self-renewal. These limitations prompted us to determine if a TSC/progenitor cell mixture would repopulate the injured airway epithelium. We developed a cell transplantation protocol and demonstrate that transplanted mouse and human tracheobronchial epithelial TSC/progenitor cell mixtures are 20-25% of airway epithelial cells, actively contribute to epithelial repair, and persist for at least 43 days. At 2 weeks after transplantation, TSCs/progenitor cells differentiated into the three major epithelial cell types: basal, secretory, and ciliated. We conclude that cell therapy that uses adult tracheobronchial TSCs/progenitor cells is an effective therapeutic option.

An Official American Thoracic Society Workshop Report: Chemical Inhalational Disasters. Biology of Lung Injury, Development of Novel Therapeutics, and Medical Preparedness

This report is based on the proceedings from the Inhalational Lung Injury Workshop jointly sponsored by the American Thoracic Society (ATS) and the National Institutes of Health (NIH) Countermeasures Against Chemical Threats (CounterACT) program on May 21, 2013, in Philadelphia, Pennsylvania. The CounterACT program facilitates research leading to the development of new and improved medical countermeasures for chemical threat agents. The workshop was initiated by the Terrorism and Inhalational Disasters Section of the Environmental, Occupational, and Population Health Assembly of the ATS. Participants included both domestic and international experts in the field, as well as representatives from U.S. governmental funding agencies. The meeting objectives were to (1) provide a forum to review the evidence supporting current standard medical therapies, (2) present updates on our understanding of the epidemiology and underlying pathophysiology of inhalational lung injuries, (3) discuss innovative investigative approaches to further delineating mechanisms of lung injury and identifying new specific therapeutic targets, (4) present promising novel medical countermeasures, (5) facilitate collaborative research efforts, and (6) identify challenges and future directions in the ongoing development, manufacture, and distribution of effective and specific medical countermeasures. Specific inhalational toxins discussed included irritants/pulmonary toxicants (chlorine gas, bromine, and phosgene), vesicants (sulfur mustard), chemical asphyxiants (cyanide), particulates (World Trade Center dust), and respirable nerve agents.

Cholesterol Interferes with the MTT Assay in Human Epithelial-Like (A549) and Endothelial (HLMVE and HCAE) Cells

Metabolically active cells are able to convert the MTT [3-(4,5-dimethythiazol-2-yl)-2,5-diphenyltetrazolium bromide] dye to blue formazan. This is the basis of the MTT assay, which is among the most widely used screening methods to evaluate cell viability and proliferation. When testing the effects of cholesterol products on the viability of human pulmonary epithelial-like A549 cells using trypan blue staining (cell numbers) and the MTT assay, results were inconsistent. The MTT assay indicated greater than 50% loss of viability with exposure of cells to cholesterol, whereas there was no decrease in viability indicated by trypan blue exclusion and propidium iodide uptake. A similar decrease in MTT reduction was obtained upon cholesterol treatment in human lung microvascular endothelial cells (HLMVECs) and human coronary artery endothelial cells (HCAECs) without loss of viability. This suggested a direct interference of cholesterol with the assay. However, using a cell-free system, there was no decrease in the reduction of MTT by ascorbic acid during incubation with a similar concentration of cholesterol. Light microscopy revealed enhanced exocytosis of formazan granules in presence of cholesterol. Incubation with apolipoprotein A-1 decreased cholesterol-mediated inhibition of MTT assay. These studies indicate decreased MTT reduction as a result of enhanced exocytosis of formazan due to cholesterol. A careful validation of viability assay procedures is therefore suggested in experiments where cholesterol is a constituent, to avoid a potential bias in concluding results of cytotoxicity studies.

Fluorescence- and bioluminescence-based approaches to study GPCR ligand binding

Ligand binding is a vital component of any pharmacologist's toolbox and allows the detailed investigation of how a molecule binds to its receptor. These studies enable the experimental determination of binding affinity of labelled and unlabelled compounds through kinetic, saturation (Kd ) and competition (Ki ) binding assays. Traditionally, these studies have used molecules labelled with radioisotopes; however, more recently, fluorescent ligands have been developed for this purpose. This review will briefly cover receptor ligand binding theory and then discuss the use of fluorescent ligands with some of the different technologies currently employed to examine ligand binding. Fluorescent ligands can be used for direct measurement of receptor-associated fluorescence using confocal microscopy and flow cytometry as well as in assays such as fluorescence polarization, where ligand binding is monitored by changes in the free rotation when a fluorescent ligand is bound to a receptor. Additionally, fluorescent ligands can act as donors or acceptors for fluorescence resonance energy transfer (FRET) with the development of assays based on FRET and time-resolved FRET (TR-FRET). Finally, we have recently developed a novel bioluminescence resonance energy transfer (BRET) ligand binding assay utilizing a small (19 kDa), super-bright luciferase subunit (NanoLuc) from a deep sea shrimp. In combination with fluorescent ligands, measurement of RET now provides an array of methodologies to study ligand binding. While each method has its own advantages and drawbacks, binding studies using fluorescent ligands are now a viable alternative to the use of radioligands. Linked Articles This article is part of a themed section on Molecular Pharmacology of G Protein-Coupled Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v173.20/issuetoc.

From the Cover: Catalytic Antioxidant Rescue of Inhaled Sulfur Mustard Toxicity

Sulfur mustard (bis 2-chloroethyl ethyl sulfide, SM) is a powerful bi-functional vesicating chemical warfare agent. SM tissue injury is partially mediated by the overproduction of reactive oxygen species resulting in oxidative stress. We hypothesized that using a catalytic antioxidant (AEOL 10150) to alleviate oxidative stress and secondary inflammation following exposure to SM would attenuate the toxic effects of SM inhalation. Adult male rats were intubated and exposed to SM (1.4 mg/kg), a dose that produces an LD₅₀ at approximately 24 h. Rats were randomized and treated via subcutaneous injection with either sterile PBS or AEOL 10150 (5 mg/kg, sc, every 4 h) beginning 1 h post-SM exposure. Rats were euthanized between 6 and 48 h after exposure to SM and survival and markers of injury were determined. Catalytic antioxidant treatment improved survival after SM inhalation in a dose-dependent manner, up to 52% over SM PBS at 48 h post-exposure. This improvement was sustained for at least 72 h after SM exposure when treatments were stopped after 48 h. Non-invasive monitoring throughout the duration of the studies also revealed blood oxygen saturations were improved by 10% and clinical scores were reduced by 57% after SM exposure in the catalytic antioxidant treatment group. Tissue analysis showed catalytic antioxidant therapy was able to decrease airway cast formation by 69% at 48 h post-exposure. To investigate antioxidant induced changes at the peak of injury, several biomarkers of oxidative stress and inflammation were evaluated at 24 h post-exposure. AEOL 10150 attenuated SM-mediated lung lipid oxidation, nitrosative stress and many proinflammatory cytokines. The findings indicate that catalytic antioxidants may be useful medical countermeasure against inhaled SM exposure.

Sulfur mustard inhalation: mechanisms of injury, alteration of coagulation, and fibrinolytic therapy

Acute lung injury due to sulfur mustard (SM) inhalation causes the formation of airway fibrin casts that obstruct airways at multiple levels, leading to acute respiratory failure and death. These pathophysiological effects are seen in rodent models of acute SM vapor inhalation, as well as in human victims of acute SM inhalation. In rat models, the initial steps in activation of the coagulation system at extravascular sites depend on tissue factor (TF) expression by airway cells, especially in the microparticle fraction, and these effects can be inhibited by TF pathway inhibitor protein. Not only does the procoagulant environment of the acutely injured lung contribute to airway cast formation, but these lesions persist in airways because of the activation of multiple antifibrinolytic pathways, including plasminogen activator inhibitor-1, thrombin-activatable fibrinolysis inhibitor, and α2-antiplasmin. Airway administration of tissue plasminogen activator can overwhelm these effects and save lives by preventing fibrin-dependent airway obstruction, gas-exchange abnormalities, and respiratory failure. In human survivors of SM inhalation, fibrotic processes, including bronchiolitis obliterans and interstitial fibrosis of the lung, are among the most disabling chronic lesions. Antifibrotic therapies may prove useful in preventing either or both of these forms of chronic lung damage.

Mutations of Vasopressin Receptor 2 Including Novel L312S Have Differential Effects on Trafficking

Nephrogenic syndrome of inappropriate antidiuresis (NSIAD) is a genetic disease first described in 2 unrelated male infants with severe symptomatic hyponatremia. Despite undetectable arginine vasopressin levels, patients have inappropriately concentrated urine resulting in hyponatremia, hypoosmolality, and natriuresis. Here, we describe and functionally characterize a novel vasopressin type 2 receptor (V2R) gain-of-function mutation. An L312S substitution in the seventh transmembrane domain was identified in a boy presenting with water-induced hyponatremic seizures at the age of 5.8 years. We show that, compared with wild-type V2R, the L312S mutation results in the constitutive production of cAMP, indicative of the gain-of-function NSIAD profile. Interestingly, like the previously described F229V and I130N NSIAD-causing mutants, this appears to both occur in the absence of notable constitutive β-arrestin2 recruitment and can be reduced by the inverse agonist Tolvaptan. In addition, to understand the effect of various V2R substitutions on the full receptor "life-cycle," we have used and further developed a bioluminescence resonance energy transfer intracellular localization assay using multiple localization markers validated with confocal microscopy. This allowed us to characterize differences in the constitutive and ligand-induced localization and trafficking profiles of the novel L312S mutation as well as for previously described V2R gain-of-function mutants (NSIAD; R137C and R137L), loss-of-function mutants (nephrogenic diabetes insipidus; R137H, R181C, and M311V), and a putative silent V266A V2R polymorphism. In doing so, we describe differences in trafficking between unique V2R substitutions, even at the same amino acid position, therefore highlighting the value of full and thorough characterization of receptor function beyond simple signaling pathway analysis.

Sarcoendoplasmic reticulum Ca(2+) ATPase. A critical target in chlorine inhalation-induced cardiotoxicity

Autopsy specimens from human victims or experimental animals that die due to acute chlorine gas exposure present features of cardiovascular pathology. We demonstrate acute chlorine inhalation-induced reduction in heart rate and oxygen saturation in rats. Chlorine inhalation elevated chlorine reactants, such as chlorotyrosine and chloramine, in blood plasma. Using heart tissue and primary cardiomyocytes, we demonstrated that acute high-concentration chlorine exposure in vivo (500 ppm for 30 min) caused decreased total ATP content and loss of sarcoendoplasmic reticulum calcium ATPase (SERCA) activity. Loss of SERCA activity was attributed to chlorination of tyrosine residues and oxidation of an important cysteine residue, cysteine-674, in SERCA, as demonstrated by immunoblots and mass spectrometry. Using cardiomyocytes, we found that chlorine-induced cell death and damage to SERCA could be decreased by thiocyanate, an important biological antioxidant, and by genetic SERCA2 overexpression. We also investigated a U.S. Food and Drug Administration-approved drug, ranolazine, used in treatment of cardiac diseases, and previously shown to stabilize SERCA in animal models of ischemia-reperfusion. Pretreatment with ranolazine or istaroxime, another SERCA activator, prevented chlorine-induced cardiomyocyte death. Further investigation of responsible mechanisms showed that ranolazine- and istaroxime-treated cells preserved mitochondrial membrane potential and ATP after chlorine exposure. Thus, these studies demonstrate a novel critical target for chlorine in the heart and identify potentially useful therapies to mitigate toxicity of acute chlorine exposure.

Physiologic Changes in the Heart Following Cessation of Mechanical Ventilation in a Porcine Model of Donation After Circulatory Death: Implications for Cardiac Transplantation

Hearts donated following circulatory death (DCD) may represent an additional source of organs for transplantation; however, the impact of donor extubation on the DCD heart has not been well characterized. We sought to describe the physiologic changes that occur following withdrawal of life-sustaining therapy (WLST) in a porcine model of DCD. Physiologic changes were monitored continuously for 20 min following WLST. Ventricular pressure, volume, and function were recorded using a conductance catheter placed into the right (N = 8) and left (N = 8) ventricles, and using magnetic resonance imaging (MRI, N = 3). Hypoxic pulmonary vasoconstriction occurred following WLST, and was associated with distension of the right ventricle (RV) and reduced cardiac output. A 120-fold increase in epinephrine was subsequently observed that produced a transient hyperdynamic phase; however, progressive RV distension developed during this time. Circulatory arrest occurred 7.6±0.3 min following WLST, at which time MRI demonstrated an 18±7% increase in RV volume and a 12±9% decrease in left ventricular volume compared to baseline. We conclude that hypoxic pulmonary vasoconstriction and a profound catecholamine surge occur following WLST that result in distension of the RV. These changes have important implications on the resuscitation, preservation, and evaluation of DCD hearts prior to transplantation.

Avoidance of Profound Hypothermia During Initial Reperfusion Improves the Functional Recovery of Hearts Donated After Circulatory Death

The resuscitation of hearts donated after circulatory death (DCD) is gaining widespread interest; however, the method of initial reperfusion (IR) that optimizes functional recovery has not been elucidated. We sought to determine the impact of IR temperature on the recovery of myocardial function during ex vivo heart perfusion (EVHP). Eighteen pigs were anesthetized, mechanical ventilation was discontinued, and cardiac arrest ensued. A 15-min standoff period was observed and then hearts were reperfused for 3 min at three different temperatures (5°C; N = 6, 25°C; N = 5, and 35°C; N = 7) with a normokalemic adenosine-lidocaine crystalloid cardioplegia. Hearts then underwent normothermic EVHP for 6 h during which time myocardial function was assessed in a working mode. We found that IR coronary blood flow differed among treatment groups (5°C = 483 ± 53, 25°C = 722 ± 60, 35°C = 906 ± 36 mL/min, p < 0.01). During subsequent EVHP, less myocardial injury (troponin I: 5°C = 91 ± 6, 25°C = 64 ± 16, 35°C = 57 ± 7 pg/mL/g, p = 0.04) and greater preservation of endothelial cell integrity (electron microscopy injury score: 5°C = 3.2 ± 0.5, 25°C = 1.8 ± 0.2, 35°C = 1.7 ± 0.3, p = 0.01) were evident in hearts initially reperfused at warmer temperatures. IR under profoundly hypothermic conditions impaired the recovery of myocardial function (cardiac index: 5°C = 3.9 ± 0.8, 25°C = 6.2 ± 0.4, 35°C = 6.5 ± 0.6 mL/minute/g, p = 0.03) during EVHP. We conclude that the avoidance of profound hypothermia during IR minimizes injury and improves the functional recovery of DCD hearts.

The lung response to ozone is determined by age and is partially dependent on toll-Like receptor 4

Background

Ozone pollution has adverse effects on respiratory health in children and adults. This study was carried out in the mouse model to investigate the influence of age and to define the role of toll-like receptor four (TLR4) in the lung response to ozone exposure during postnatal development.

Methods

Female mice (1 to 6 weeks of age) were exposed for 3 h to ozone (1 part per million) or filtered air. Analyses were carried out at six and 24 h after completion of exposure, to assess the effects on lung permeability, airway neutrophilia, expression of antioxidants and chemokines, and mucus production. The role of TLR4 was defined by examining TLR4 expression in the lung during development, and by investigating the response to ozone in tlr4-deficient mice.

Results

Metallothionein-1, calcitonin gene-related product, and chemokine C-X-C ligand (CXCL) five were consistent markers induced by ozone throughout development. Compared with adults, neonates expressed lower levels of pulmonary TLR4 and responded with increased mucus production, and developed an attenuated response to ozone characterized by reduced albumin leakage and neutrophil influx into the airways, and lower expression of CXCL1 and CXCL2 chemokines. Examination of the responses in tlr4-deficient mice indicated that ozone-mediated airway neutrophilia, but not albumin leakage or mucus production were dependent on TLR4.

Conclusions

Collectively, the data demonstrate that the response to ozone is determined by age and is partially dependent on TLR4 signaling. The reduced responsiveness of the neonatal lung to ozone may be due at least in part to insufficient pulmonary TLR4 expression.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-015-0279-2) contains supplementary material, which is available to authorized users.

Chlorine inhalation-induced myocardial depression and failure

Victims of chlorine (Cl2) inhalation that die demonstrate significant cardiac pathology. However, a gap exists in the understanding of Cl2-induced cardiac dysfunction. This study was performed to characterize cardiac dysfunction occurring after Cl2 exposure in rats at concentrations mimicking accidental human exposures (in the range of 500 or 600 ppm for 30 min). Inhalation of 500 ppm Cl2 for 30 min resulted in increased lactate in the coronary sinus of the rats suggesting an increase in anaerobic metabolism by the heart. There was also an attenuation of myocardial contractile force in an ex vivo (Langendorff technique) retrograde perfused heart preparation. After 20 h of return to room air, Cl2 exposure at 500 ppm was associated with a reduction in systolic and diastolic blood pressure as well echocardiographic/Doppler evidence of significant left ventricular systolic and diastolic dysfunction. Cl2 exposure at 600 ppm (30 min) was associated with biventricular failure (observed at 2 h after exposure) and death. Cardiac mechanical dysfunction persisted despite increasing the inspired oxygen fraction concentration in Cl2-exposed rats (500 ppm) to ameliorate hypoxia that occurs after Cl2 inhalation. Similarly ex vivo cardiac mechanical dysfunction was reproduced by sole exposure to chloramine (a potential circulating Cl2 reactant product). These results suggest an independent and distinctive role of Cl2 (and its reactants) in inducing cardiac toxicity and potentially contributing to mortality.

Nitrogen mustard exposure of murine skin induces DNA damage, oxidative stress and activation of MAPK/Akt-AP1 pathway leading to induction of inflammatory and proteolytic mediators

Our recent studies in SKH-1 hairless mice have demonstrated that topical exposure to nitrogen mustard (NM), an analog of sulfur mustard (SM), triggers the inflammatory response, microvesication and apoptotic cell death. Here, we sought to identify the mechanism/s involved in these NM-induced injury responses. Results obtained show that NM exposure of SKH-1 hairless mouse skin caused H2A.X and p53 phosphorylation and increased p53 accumulation, indicating DNA damage. In addition, NM also induced the activation of MAPKs/ERK1/2, JNK1/2 and p38 as well as that of Akt together with the activation of transcription factor AP1. Also, NM exposure induced robust expression of pro-inflammatory mediators namely cyclooxygenase 2 and inducible nitric oxide synthase and cytokine tumor necrosis factor alpha, and increased the levels of proteolytic mediator matrix metalloproteinase 9. NM exposure of skin also increased lipid peroxidation, 5,5-dimethyl-2-(8-octanoic acid)-1-pyrroline N-oxide protein adduct formation, protein and DNA oxidation indicating an elevated oxidative stress. We also found NM-induced increase in the homologous recombinant repair pathway, suggesting its involvement in the repair of NM-induced DNA damage. Collectively, these results indicate that NM induces oxidative stress, mainly a bi-phasic response in DNA damage and activation of MAPK and Akt pathways, which activate transcription factor AP1 and induce the expression of inflammatory and proteolytic mediators, contributing to the skin injury response by NM. In conclusion, this study for the first time links NM-induced mechanistic changes with our earlier reported murine skin injury lesions with NM, which could be valuable to identify potential therapeutic targets and rescue agents.

Intratracheal heparin improves plastic bronchitis due to sulfur mustard analog

BACKGROUND

Inhalation of sulfur mustard (SM) and SM analog, 2-chloroethyl ethyl sulfide (CEES), cause fibrinous cast formation that occludes the conducting airways, similar to children with Fontan physiology-induced plastic bronchitis. These airway casts cause significant mortality and morbidity, including hypoxemia and respiratory distress. Our hypothesis was that intratracheal heparin, a highly cost effective and easily preserved rescue therapy, could reverse morbidity and mortality induced by bronchial cast formation.

METHODS

Sprague-Dawley rats were exposed to 7.5% CEES via nose-only aerosol inhalation to produce extensive cast formation and mortality. The rats were distributed into three groups: non-treated, phosphate-buffered saline (PBS)-treated, and heparin-treated groups. Morbidity was assessed with oxygen saturations and clinical distress. Blood and bronchoalveolar lavage fluid (BALF) were obtained for analysis, and lungs were fixed for airway microdissection to quantify the extent of airway cast formation.

RESULTS

Heparin, given intratracheally, improved survival (100%) when compared to non-treated (75%) and PBS-treated (90%) controls. Heparin-treated rats also had improved oxygen saturations, clinical distress and airway cast scores. Heparin-treated rats had increased thrombin clotting times, factor Xa inhibition and activated partial thromboplastin times, indicating systemic absorption of heparin. There were also increased red blood cells (RBCs) in the BALF in 2/6 heparin-treated rats compared to PBS-treated control rats.

CONCLUSIONS

Intratracheal heparin 1 hr after CEES inhalation improved survival, oxygenation, airway obstruction, and clinical distress. There was systemic absorption of heparin in rats treated intratracheally. Some rats had increased RBCs in BALF, suggesting a potential for intrapulmonary bleeding if used chronically after SM inhalation.

Topical nitrogen mustard exposure causes systemic toxic effects in mice

Vesicating agents sulfur mustard (SM) and nitrogen mustard (NM) are reported to be easily absorbed by skin upon exposure causing severe cutaneous injury and blistering. Our studies show that topical exposure of NM (3.2mg) onto SKH-1 hairless mouse skin, not only caused skin injury, but also led to significant body weight loss and 40-80% mortality (120 h post-exposure), suggesting its systemic effects. Accordingly, further studies herein show that NM exposure initiated an increase in circulating white blood cells by 24h (neutrophils, eosinophils and basophils) and thereafter a decrease (neutrophils, lymphocytes and monocytes). NM exposure also reduced both white and red pulp areas of the spleen. In the small intestine, NM exposure caused loss of membrane integrity of the surface epithelium, abnormal structure of glands and degeneration of villi. NM exposure also resulted in the dilation of glomerular capillaries of kidneys, and an increase in blood urea nitrogen/creatinine ratio. Our results here with NM are consistent with earlier reports that exposure to higher SM levels can cause damage to the hematopoietic system, and kidney, spleen and gastrointestinal tract toxicity. These outcomes will add to our understanding of the toxic effects of topical vesicant exposure, which might be helpful towards developing effective countermeasures against injuries from acute topical exposures.

Antifibrinolytic mechanisms in acute airway injury after sulfur mustard analog inhalation

Acute lung injury in response to mustard gas (sulfur mustard [SM]) inhalation results in formation of fibrin casts, which obstruct the airway. The objective of this study was to identify fibrinolytic pathways that could be contributing to the persistence of airway casts after SM exposure. Rats were exposed to the SM analog, 2-chloroethyl ethyl sulfide, via nose-only aerosol inhalation. At 4 and 18 hours after exposure, animals were killed and airway-capillary leak estimated by measuring bronchoalveolar lavage fluid (BALF) protein and IgM content. The fibrin clot-degrading and plasminogen-activating capabilities of BALF were also assessed by activity assays, whereas Western blotting was used to determine the presence and activities of plasminogen activator inhibitor-1, thrombin activatable fibrinolytic inhibitor and α2-antiplasmin. Measurement of tissue-specific steady-state mRNA levels was also conducted for each fibrinolytic inhibitor to assess whether its synthesis occurs in lung or at extrapulmonary sites. The results of this study demonstrate that fibrin-degrading and plasminogen-activating capabilities of the airways become impaired during the onset of 2-chloroethyl ethyl sulfide-induced vascular leak. Findings of functionally active reservoirs of plasminogen activator inhibitor-1, thrombin activatable fibrinolysis inhibitor, and α2-antiplasmin in BALF indicate that airway fibrinolysis is inhibited at multiple levels in response to SM.